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    說明:專業詞準確,英文地道
    多媒體技術
    Multimedia Technology
    作者:佚名
    譯者:佚名
    1.多媒體的出現
    1. 信息技術發展趨勢(用戶觀點)
    要了解多媒體計算背后的動因,有必要從最終用戶(相對于技術人員)角度考察一下信息技術。對于最終用戶來講,信息技術關心的是能訪問各種形式的信息并能通過這些各種形式的信息進行協作(共同完成任務)。任何一種有益于完成這一任務的實際技術在最終用戶看來只不過是一種工具而已。
    從這一角度來看,我們有可能把信息技術從兩個不同的方面表達:即最終用戶可用的媒體形式進行有效通信的能力?,F代信息用戶在這兩方面都面臨著越來越大的壓力。這些壓力將在下面更為詳細地討論。
    1.1.1 媒體形式
    這些年來,用于傳輸信息的媒體范圍增加了許多。早先,通信僅限于簡單形式的媒體如聲音和紙張。但在本世紀,引入了大量的不同的媒體類型,如電話和可視媒體。本世紀末,這種趨勢在加劇。目前,可用于傳輸信息的媒體類型范圍很廣。
    這方面的進展為諸如教育和商業這樣的領域提供了許多新的發展機會。但是,同時也存在著與社會信息激增有關的一系列問題。尤其是存在著很大的產生信息過量的危險。這個問題在商務活動中能夠見到:例如,行政決策者們必須根據不斷增加的大量的各種各樣的信息做出決策。類似的問題同樣也出現在象政府、醫療和教育部門。
    1.1.2 通信問題
    從用戶角度講,信息技術更進一步的發展趨勢是信息的分散化?,F代的多數機構組織都非常龐大并且越于由若干個散布在廣大范圍的地區的許多分支機構構成。這些分支機構常常通過共享的交換信息而協同工作。這樣,通信對大多數機構來講就非常關鍵。高效的通信能使成功與失敗差別巨大。沒有適合的通信形式,就存在著信息匱乏的危險。也就是,決策者們沒有恰當的信息用于做出正確的決策。
    1.1.3 信息技術的需求
    因此,最終用戶面臨著兩個問題:信息過量和信息匱乏。他們要么擁有太多的信息,要么沒有恰當的信息,也因此需要幫助最終用戶管理信息以便減輕由不斷增加的信息重要性所產生的負擔。本質上講,最終用戶需要的是在恰當的時間把恰當的信息提供給適當的人。
    顯然這一點不能借于手工系統來完成。這樣就必須使信息管理過程的自動化。
    1.2 信息技術發展趨勢(系統觀點)
    從系統觀點來看,信息技術關心的是信息的處理和在不同的位置進行信息通信的能力。更為特別的是,信息技術被認作為是計算技術和通信基礎的結合。 這項技術的目標實質是為最終用戶管理信息。
    從系統角度看,信息技術最為顯著的發展趨勢就是不斷地使媒體集成。傳統上,計算機系統僅僅處理數值計算。但是,隨后文本處理變為計算機設計得們一個非常關心的問題。通信技術也被開發成能夠支持文本和數值數據的傳輸,近來,計算機和通信能夠支持的媒體類型激增,有關把圖形集成到計算機工作站和通信技術的工作已取得重要進展,研究人員正在著手解決由音頻和視頻所產生的更為辣手的問題。

    2.什么是多媒體
    上一節既從用戶角度又從系統角度強調了信息技術的一些重要發展趨勢。從這些討論里已引出兩個主題。首先信息類型的式樣性是現代信息系統的重要特征。其次,為處理多樣性,集成是關鍵。這些觀察結果為多媒體提供了一個很生動的定義:
    多媒體=多樣性+集成
    多媒體系統必須支持各種媒體類型。這里包括象文本和圖形這樣平常的媒體也包括象動畫、音頻和視頻這樣豐富的媒體。但是,只有這一點對于多媒體環境是不夠的。同樣重要的是,要把各種媒體類型源集成到單個系統框架內。因而,一個多媒體系統就是這樣一個系統:它允許最終用戶以集成的方式共享、通信和處理各種形式的信息。
    實質上,多媒體系統是試圖通過把各種形式的媒體集成到計算機/通信基礎設施中來解決信息管理問題。達到這一層次集成的好處有兩點:
    ·計算機能幫助完成管理和處理信息的任務
    ·信息用戶只須與單個集成環境而不是和許多分離的信息子系統打交道
    這就是多媒體信息系統的最大優勢,也是當前有關研究背后的主要動因。

    3.多媒體技術
    當初我們在屏幕上只看到文本時,基本的用戶接口是DOS提示或者可能是一個簡單的選擇表。既然我們現在同時有圖形和文本, 我們就可以有一更直觀的、鼠標驅動的、基于圖形的外加下拉式菜單的用戶接口,如同在Macintosh、Microsoft
    Windows和Presentation Manager中那樣的用戶接口。當我們可以加進質量如照片的圖像、動畫、優質聲音和具有交互性時,我們就應該有能力使計算機功能更強和更易使用。
    這就是多媒體這個最新術語背后的概念。多媒體一般是指圖形、動畫、光存儲、圖象處理和聲音的合成,不是指單一技術、產品或市場。相反它是多種技術的集合,擁護者認為總有一天這些技術能融合在一起。迄今,多媒體的多數活動發生在Macintosh和Amiga
    機上,因為它們具有內置的圖形和聲音功能,但你有希望看到這種技術會擴散到其它平臺上。
    今天,被當作多媒體的各種技術定義了很多獨立的小類別。
    其中最重要的是動畫,其功能是在你的屏幕上移動圖像。動畫又與另一種叫做臺式視頻的概念緊密相連,實際是生成和視頻圖像、生成室內演示片、商業視頻錄相的草稿或培訓產品。
    在多媒體演示中聲音也將起關鍵作用。
    視頻圖像也占了很多磁盤空間。為了解決這個問題,尤其是隨著可擦寫光盤成為主流產品,有些團體期待著光盤存儲。
    臺式視頻圖像和動畫都不錯,但很多支持者看中的是把所有這些單元結合成為一個交互系統(即交互多媒休或稱作超級媒體)的方式。
    此概念是讓用戶選擇多媒體演示的走向,要能很容易地從一個單元移向另一單元。設想一個電影,你能控制下一步要發生什么。
    傳統的計算機語言完成此任務太難了,也許包含超級文本系統的面向目標的編程系統能發揮作用。
    當然,Apple公司看中的Hypercard作為這種系統的核心萬分。這是有些道理的。Hypercard符合很多基本準則:它被設計成可以定制的,能把各種類型的信息聯接和混合在一起,這些信息包括文本、圖形和動畫。
    這不是說現在不存在此技術的市場了。多媒體應用從專業水準的視頻圖像制作到公司圖片演示、工種視算化,更好更簡易的培訓和計算機輔助教學產品等所有方面都有有具體用途。但你可以看到這些市場將更為專門、而不是大眾化的,它介乎于CAD與臺式出版之間。
    讓我們這樣來看,使用計算機仍比開車或讀報困難。在某種理想化的未來,它應更為強大,但利用多媒體技術,也更易使用。

    4.什么是多媒體PC機
    什么是MPC?它是“多媒體個人計算機”的縮寫。它意味著你的計算領域已開始發生永久性變化,并變得越來越好。你知道你有很好的理由在家里擁有一臺具有事務處理能力的PC機。它幫助你完成繁重的工作任務,否則這些任務將迫使你留在辦公室里開夜車。
    但是,當你不工作時,你在這些強大的家用PC機上能干些什么呢?這正好可讓多媒體加入。在今天的家用PC機上增加立體聲、CD-ROM光盤機和Windows操作系統相對而言是便宜的,而且也較容易。然而,你最覆蓋得到的是遠比一臺能說話、能播放光盤和能顯示美麗圖像的計算機更為革命性的東西。你的多媒體PC機(為簡單起見,簡稱為MPC)成了完成以下諸活動的關鍵:它能發現通過圖像和話音將思想帶入實際生活的書籍和百科全書;發現與最好的街道娛樂質量和趣味相媲美的游戲;以及發現能發揮的音樂、動畫和視頻圖形方面個人創造力的軟件。
    對一臺MPC機的要求在Microsoft公司的《多媒體PC機規范第1.0版》一書中有詳細的描述。下面是此規范的要點:
    基本系統:一臺能運行Windows操作系統訴系統,它采用10MHZ時鐘的286或速度更快的CPU;至少有2兆字節的RAM;30兆字節或更大容量的硬盤;3.5英寸1.44兆字節的軟盤機;101鍵的鍵盤;兩按鈕的鼠標器以及并行、串行的控制桿端口。
    視頻顯示:一般總是要求用VGA顯示;特別推薦使用VGA+(標準VGA分辨率的8位彩色)。
    CD-ROM:要求CD-ROM光盤機的數據傳輸出率至少為每秒150K,不能占用40%以上的CPU時間,能放出光盤的音頻,平均存取時間為一秒或更短。
    聲頻功能:一塊8位的、11.025KHZ取樣和22.05KHZ放聲卡;能放出8個同時使用五種不同音色的音律的合成器;把光盤聲頻、取樣和合成聲音混合起來的混聲器;麥克風輸入;MIDI(樂器數字接品)輸入、輸出和通路。
    第一種新技術都有它自己的術語,將它們進行分類是一項真正精細的工作,下面是MPC的兩個術語。
    全動圖像:全動圖像是數字記錄的視頻圖像,以每秒30幀的電視廣播標準或者以非常接近于此的速度重現圖像,因而這些視頻圖像看上去很自然,沒有跳躍感。
    MIDI:MIDI是樂器數字接口的縮寫,它是由音樂合成器制造商開發的標準規范。從一個鍵盤能控制幾個樂器的概念已發展成一種方法,它能把樂器、磁帶錄音機、錄像機、混聲器、甚至舞臺燈光都置于單臺計算機的控制之下。
    1. The Emergence of Multimedia
    1.1 Trends in information technology (a user perspective)
    To understand the motivation behind multimedia computing, it is important
    to consider information technology from the point of view of the end user
    (as opposed to the technologist). To an end user, information technology
    is concerned with access to various forms of information and the ability
    to cooperate through these forms of information. Any actual technology
    which helps in this task is merely a means to an end.
    From this perspective, it is possible to identify two separate aspects
    of information technology, namely the forms of media available to an end
    user and the ability to efficiently communicate using these media forms.
    In both these areas, the modern user of information is coming under increased
    pressure. These pressures are discussed in more details below.
    1.1.1 forms of media
    In recent years, there has been a dramatic increase in the range of media
    used to convey information. Initially, communication was limited to simple
    forms of media such as voice and paper. This century, however, has witnessed
    the introduction of a greater variety of media types such as the telephone
    and visual forms of media. In the latter part of the century, this trend
    has accelerated and there is now a wide range of media types available
    to convey information.
    These advances provide a great opportunity for new developments in a range
    of areas such as education and commerce. However, there are also a number
    of problems associated with the growth of information in society. In particular,
    there is a great danger of creating information overload. This problem
    can be seen, for example, in business where executives are required to
    make decisions based on an ever increasing variety and volume of information.
    Similar problems are also occurring in areas such as government, health
    care and education.
    1.1.2 Problems of communication
    A further trend in information technology from a user perspective is the
    decentralization of information. Most modern organizations are very large
    and tend to consist of a number of separate institutions typically cooperate
    through the sharing and exchange of information. Thus, communication is
    a vital concern for most organizations and efficient communications can
    make the difference between successful operation and failure. Without the
    appropriate forms of communication. There is a danger of information starvation,
    i. e. decision makers do not have the right information to make the correct
    decisions.
    1.1.3 Requirements for information technology
    The end user is therefore faced with the two problems of information overload
    and information starvation. They may either have too much information of
    may not have the right information. There is therefore a need to help the
    end user to manage information to ease the burden created by the increasing
    importance of information. essentially, the end user needs support to get
    the right information to the right people at the right time. This clearly
    cannot be achieved by manual systems. Thus, there is a requirement for
    automation in the process of information management.
    1.2 Trends in information technology (a systems perspective)
    From a systems perspective, information technology is concerned with the
    processing of information and the ability to communicate information between
    different sites. More specifically, information technology is seen as a
    combination of computing technology and communications infrastructures.
    The aim of this technology is essentially to manage information for the
    end user.
    The most noticeable trend in information technology from a system perspective
    has been the increasing integration of media. Traditionally, computer systems
    dealt exclusively with numerical calculations. However, text processing
    soon became an important concern for computer designers. Communications
    technologies were also developed to support the transmission of textual
    and numerical data. More recently, there has been a dramatic increase in
    the range of media types supported by computers and communications technologies.
    Significant steps have been taken in integrating graphics into computer
    workstations and communications technology. Researchers are now tackling
    the harder problems presented by audio and video.

    2.What is Multimedia?
    The previous section has highlighted important trends in information technology
    from both the end user and technology perspective. Two themes have emerged
    from this discussion. Firstly, the variety of media types is an important
    feature of modern information systems. Secondly, in order to deal with
    the variety, integration is a critical concern. These observations provide
    a good working definition of multimedia:
    MULTIMEDIA=VARIETY+INTEGRATION
    It is necessary for a multimedia system to support a variety of media types.
    This could be as modest as text and graphics or as rich as animation, audio
    and video. However, this alone is not sufficient for a multimedia environment.
    It is also important that the various sources of media types are integrated
    into a single system framework. A multimedia system is then one which allows
    end users to share, communicate and process a variety of forms of information
    in an integrated manner.
    In essence, multimedia systems are attempting to solve the problems of
    information management by integrating the various forms of media into the
    compute/communications infrastructure. There are two benefits of achieving
    this level of integration:
    · the computer can help in the task of managing and processing the information.
    · information user only have to deal with one integrated environment rather
    than a number of separate information subsystems.
    This is the great benefit of multimedia information systems and is the
    main motivation behind the current research on the subject.

    3.Multimedia Technology
    When we just had text on screen, the basic user interface was a DOS prompt
    or maybe a simple list of choices. Now that we have graphics and text at
    the same time, we can have a much more intuitive mouse-driven graphics
    based user interface with pulldown menus, as in the Macintosh, Microsoft
    Windows, and Presentation Manager. When we can add photograph-quality images,
    animation, good-quality sound, and interactivity, then we ought to be able
    to make computers much more powerful-and much easier to use.
    That's the concept behind Multimedia, the newest buzzword. Multimedia,
    which typically refers to a synthesis of graphics, animation, optical storage,
    image processing, and sound, is not a single technology, product, or market.
    Instead, it is a collection of technologies that proponents believe will
    one day be joined together. So far, most of the activity in Multimedia
    has taken place on the Macintosh and on the Amiga because of their built-in
    graphics and sound features but you can expect this technology to spread
    to other platforms.
    Today, the various technologies referred to as Multimedia define a number
    of individual niches.
    One of the most important of these is animation, the capability to have
    moving images on your screen.
    Animation is tightly tied in with another concept called desktop video
    — actually creating and manipulating video images, to produce in-house
    presentations, rough drafts of commercial videos, or training products.
    Sound will also play a key role in multimedia presentations.
    Video images also take up a lot of disk space. To handle this, some groups
    are looking at optical discs for storage, particularly as erasable optical
    media become more mainstream.
    Desktop video and animation is all well and good, but what many proponents
    see is a way of combining all these elements into an interactive system
    — interactive multimedia or hypermedia.
    The concept is to let a user select the direction of a multimedia presentation,
    easily moving from one element to another. Imagine a movie in which you
    can control what happens next.
    Traditional computer languages are far too difficult for this task; perhaps
    an object-oriented programming system that includes a hypertext system
    would work.
    Apple, of coures, sees Hypercard as the core element in such a system.
    This makes a certain amount of sense. Hypercard fits many of the basic
    criteria: It was designed to be customizable, capable of linking information
    and incorporating all kinds of information, including text, graphics, and
    animation.
    That's not to say there aren't already markets for this technology. Multimedia
    applications have specific uses all over the spectrum, from professional-quality
    video production to corporate presentations to engineering visualization
    to better and easier training and computer-aided instruction products.
    But you can expect these markets to be more targeted (vertical) than mass
    marketed, somewhere between CAD and desktop publishing.
    Let's look at it this way: Using a computer is still more difficult than
    driving a car of reading a newspaper. In some ideal future, it should be
    still more powerful — but, with multimedia techniques, much easier to use.

    4.What is MPC?
    What is MPC? MPC stands for "multimedia personal computer". What it means
    that your computing universe has just changed, forever and for the better.
    You know you have good reason to own a business-strengh PC at home. It
    helps you complete the work chores that otherwise would keep you burning
    the midnight oil back at the office.
    But what can you do with your home PC powerhouse when you're not working?
    That's where multimedia comes in. It's relatively cheap and easy to add
    stereo sound, a CD-ROM drive, and Windows to today's work-at-home PC. What
    you end up with, though, is something far more revolutionary than just
    a computer that talks, plays compact discs, and displays pretty pictures.
    Your multimedia PC — MPC, for short — is the key to discovering books and
    encyclopedias that bring ideas to life through images and speech, games
    that match the quality and fun of the best arcade entertainment, and software
    that unleashes your personal creativity in music, animation, and video.
    The requirements for an MPC are described in detail in Microsoft's Multimedia
    PC Specification Version 1.0. Here are the key elements of the spec:
    BASE SYSTEM: A Windows-capable system with a 10-MHz 286 or faster CPU;
    at least 2MB of RAM; a 30-MB or larger hard disk; a 3.5-inch 1.44-MB floppy
    drive; a 101-key keyboard; a two-button mouse; and parallel, serial, and
    joystick ports.
    VIDEO: Standard VGA is all that's required; VGA+(8bit color at standard
    VGA resolution) is strongly recommended.
    CD-ROM: A CO-ROM drive that transfers at least 150K of data per second
    without taking up more than 40 percent of the CPU's attention, plays CD
    audio, and has an average access time of 1 second or less.
    AUDIO: A sound board with 8-bit, 11.025-KHz sampling and 22.05-KHz playback;
    a synthesizer capable of playing eight notes simultaneously using five
    different sounds; a mixer to combine CD audio, sampling, and synth; a microphone
    input; and MIDI in, out, and thruports.
    Every new technology has its own buzzwords, and sorting them out can be
    real detective work. The following is two jargons of MPC.
    FULL-MOTION VIDEO
    Full-motion video is digitally recorded video played back at the broadcast
    standard of 30 frames per second, or close enough to that speed so the
    video appears smooth rather than jerky.
    MIDI
    MIDI is short for Musical Instrument Digital Interface, a standard specification
    developed by music synthesizer manufacturers. The concept of being able
    to control several instruments from one keyboard has grown into a method
    for putting musical instruments, tape recorders, VCRs, mixers, and even
    stage-lighting under the control of a single computer.
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